1. Field of the Invention
The present invention relates to a probe (a contact) of a prober device used for circuit inspection of plural semiconductor chips formed on a wafer in a production process of an electronic device such as LSI. More particularly, the present invention relates to a probe structure of a prober device used for a probing test that collectively measures electrical continuity of semiconductor chips by vertical probes brought into contact with circuit terminals (pads) arranged on the semiconductor chips in a wafer state.
2. Description of Prior Art
Along with the development of semiconductor technology, the integration degree of electronic devices is increasing. An area occupied by the circuit wiring is increasing in each semiconductor chip formed on a wafer and the number of circuit terminals (pads) on each semiconductor chip is also increasing. Under such circumstances, miniaturization of pad arrangement is pursued by reducing the pad area and narrowing the pad pitch, and the like. At the same time, a chip size package (CSP) is increasingly used where semiconductor chips are mounted as bear chips on a circuit board or other substrate, without being placed in a package. For this reason, it is inevitably necessary to check characteristics and determine quality in the wafer state before dividing into semiconductor chips.
An example of the semiconductor chip inspection method is that plural needle probes each having an elastically deformed portion that elastically deforms under an external force are arranged in area array to form a contact assembly, and then the contact assembly is interposed between pads of semiconductor chips to be inspected and an inspection apparatus. A printed wiring board called a probe card is used as means for electrically connecting the contact assembly and the inspection circuit of the semiconductor chips.
An issue arising out of the miniaturization of pad arrangement (narrowing of pitch) is that the probe structure needs to be made suitable for the miniaturization of pad arrangement to establish electrical continuity by bringing into contact with the pads of the semiconductor chips in the electrical characteristics test and circuit inspection of electronic devices. In order to address the increasingly miniaturized pad arrangement, various types of measurement methods are used.
An example of the probe structure is a needle probe having a cantilever structure. However, the cantilever structure has had the following problems. The pad is damaged as an end of the probe is displaced in the horizontal direction when coming into contact with the pad, and the measurement yield decreases as the end deviates from the pad. There has been another problem that it is difficult to control the contact pressure to be constant due to variation of the fitting accuracy of each probe.
In a vertical probe replacing the cantilever structure, more specifically, in a vertical probe that is vertically fixed to a circuit terminal of a probe card, it is necessary to configure that the pad pitch on the semiconductor chip and the circuit terminal pitch on the probe card have the same pitch interval. However, there is technical limitation to miniaturization of the circuit pattern on the probe card which is the printed wiring board. Thus, it is difficult to meet the requirement of matching the pad pitch in relation to the area occupied by the circuit terminals and to the wiring width. Further, the pitch interval available for soldering is also limited, so that it has not been possible to vertically fix the vertical probe to the probe card in line with the pad pitch of the semiconductor chip as the miniaturization has progressed. There has been another problem that a scrubbing function described below is not operated.
A pad of an IC chip to be inspected is generally formed by an aluminum alloy film or a gold plate. The surface of the pad is covered with an oxide film or other material. In order to establish stable electrical continuity between the probe and the pad, the vertical probe has a function that, upon contact of the end of the probe with the pad, as shown in FIG. 14A described below, the probe pin end is pressed (overdriven) by a certain distance in the vertical direction after coming into contact with the pad, while rubbing (scrubbing) the surface of the pad in the horizontal direction to destroy the oxide film or other material.
In order to realize the requirement of the probe pin structure as described above, namely, in order to adapt to the miniaturization of pad arrangement and the narrowing of pitch as well as to realize precise control of behavior in the vicinity of the contact portion of the probe including overdrive and scrubbing functions, the inventors have made the following proposition.
A conventional example proposed by the inventors will be described with reference to FIGS. 14A to 14C. FIGS. 14A to 14C are views illustrating a probe in the cantilever structure and parallel spring structure according to the conventional invention. FIGS. 14A, 14B, 14C are views showing the movement of the end portion of each probe. Incidentally, the end of the probe is kept vertical until coming into contact with a pad portion of a semiconductor chip and the like.
In FIG. 14A, a vertical probe 202a is attached to an end portion of a cantilever 201 having a length L. The vertical probe 202a has an end portion vertically facing an upper surface of a pad 203 of a semiconductor chip and the like, and the other end horizontally attached to a support portion 204. Next, when the pad 203 is raised or the support portion 204 is lowered for inspection, the end portion of the vertical probe 202a and the upper surface of the pad 203 come into contact with each other. The cantilever 201 of the length L is rotated about a calculated position of approximately (⅓) L. The end portion of the vertical probe 202a largely moves by a distance d0 while contacting the upper surface of the pad 203. As a result, particularly for miniaturized pads, the end portion of the vertical probe 202a deviates from the pad portion 203, and so the measurement may be disabled. Further, the upper surface of the pad 203 may be scratched or damaged when a large pushing pressure is applied to the vertical probe end, which would lead to the decrease of the yield of the assembly and testing process such as wire bonding.
In order to eliminate such negative effects, as shown in FIG. 14B, the cantilever 201 has a link structure of a parallel spring 205 in which a vertical probe 202b is provided at an end of the link 205. With such a link structure, when a contact load is applied to the vertical probe 202b in the same vertical direction as shown in FIG. 14A, the move distance d1 of the end portion of the vertical probe 202b is d1<d0. Thus the move distance can be limited to a very small amount due to the link structure.
The parallel spring is formed by plural beams having substantially the same shape and being arranged parallel to each other. The plural beams are fixed at both ends thereof to common deformable supports. When the support on one side is fixed and the support on the other side is moved, the beams perform translation movement within a certain range.
FIG. 14C shows a link structure in which the shape of the parallel spring 205 forming the cantilever is deformed in advance. The move distance d2 of the end portion of the vertical probe 202c is d2<d0. Thus the move distance can also be limited to a very small amount.
As described above, the precise control of behavior has been made possible in the vicinity of the contact portion between the pad and the probe, by employing the probe structure of the parallel spring structure instead of the cantilever structure used in the past, and by selecting the shape, size, material, and the like.
A conventional example using the parallel spring will be described with reference to FIGS. 15A to 15C. FIGS. 15A, 15B, 15C are views respectively showing the relationship between the pad and the end portion of the probe using the parallel spring. In FIG. 15A, the parallel beams of the probe are in a horizontal state until the pad 213 relatively moves in the vertical direction and comes into contact with the end portion of the vertical probe 212. Next, as shown in FIG. 15B, the pad starts to come into contact with the end portion of the vertical probe 212. When a movement is applied to pushup the probe in the vertical direction by a certain amount, namely, when overdrive is applied to the probe, two parallel beams 211a, 211b of the probe rotate and move substantially in parallel to each other. Along with this, the vertical probe 212 moves in the vertical direction. At this time, the vertical probe 212 moves in the vertical direction while moving in the horizontal direction along the contact surface of the pad 213 by the distance d1. The move distance can be set to a value sufficiently smaller than the move distance of the end of the vertical probe having the cantilever structure used in the past as shown in FIG. 14A, thereby preventing the probe end from deviating from the pad 213. The oxidized film or other material existing on the surface of the pad 213 is destroyed by the horizontal movement of the probe contact end. In this way, stable electrical continuity can be established between the probe 212 and the pad 213. After the inspection is completed, as shown in FIG. 15C, the pad and the probe are released from the pushing pressure and returned to their original state.